1. Field of the Invention
The present invention relates to a process and device for measuring the initial permeability of ferrimagnetic materials over a large frequency band, as a function of temperature.
2. Description of the Prior Art
Fundamental and applied research on ferrimagnetic materials used in the area of electronics and telecommunications require determination of the frequency spectrum of the initial permeability as a function of temperature, the initial permeability corresponding to a tangent to the origin of the first magnetizing curve.
Such determination is traditionally performed by measuring impedance on circuits with localized constants or distributed constants depending on the frequency range considered.
At the bottom of the frequency range, these measurements are made by impedance bridges; the range 50 Hz to 160 MHz can be covered by using several different instruments. Such measurements using bridges are in any case long and meticulous, furthermore, when working as a function of temperature, the connection obligations due to the use of a cryostatic system means that the measurements become very difficult if not impossible, above a few tenths of MHz.
Above 160 MHz, impedance is measured by hyperfrequency methods: admittance bridge or split line. It is nearly impossible to adapt these very long and delicate measurements to thermal variations.